Playlist: http://www.youtube.com/view_play_list...Find out more: http://www.bbc.co.uk/naturesgreateventsEvery year grizzly bear families in North America depend for their survival on a spectacular natural event: the return of hundreds of millions of salmon from the Pacific Ocean to the mountain streams where they were born. In this clip, dozens of hungry bears eagerly await the salmon that make it up river.